1. The power supply voltage is normal, but the motor does not start after being powered on
1) The power wiring is open (the motor has no sound at all). There should be no voltage at both ends of the measuring terminal.
2) The main winding or auxiliary winding is open circuited. The method of measuring DC resistance can determine whether there is an open circuit.
3) The centrifugal switch contacts are not closed, which prevents the auxiliary winding from being powered on and working. Disconnect the connection point between the main winding and the auxiliary winding, and then determine it by measuring the DC resistance, or by using the method in Part 2.
4) Open circuit or internal open circuit in the wiring of the starting capacitor. The search method is the same as item 3) above.
5) For covered pole motors, the covered pole coil (short-circuit ring) is open or detached. For the setting of short-circuit rings that can be seen externally, it is often discovered through observation, otherwise the method in the second part can be used to determine.
6) For series excited motors, if the electric brush is not connected or cannot make contact with the commutator due to short or stuck electric brushes, or if the electric brush lead is disconnected, or if there is an open circuit inside the armature winding or magnetic field winding.
 
2. The power supply voltage is normal. After being powered on, the motor rotates at low speed with a "buzzing" sound and vibration sensation, and the current does not decrease
1) Overloaded.
2) The stator and rotor of the electric motor rub against each other. It will make abnormal friction sounds.
3) Bearing jamming can be caused by poor assembly of the bearing, solidification of grease inside the bearing, or damage to the bearing roller bracket or rollers.
4) For series excited motors, short circuits between commutator segments or internal short circuits in armature windings, or excessive deviation of brushes from the centerline (for motors with movable brushes).
 
After being powered on, the power fuse quickly melts
1) Serious short circuit between winding turns or to ground. Measure the DC resistance. If the value is much lower than the normal value, it is a winding turn to turn short circuit; Severe ground short circuits can be measured and determined using an insulation resistance meter or multimeter with a higher resistance range (such as R × 1k range). The current will be greater than the rated value.
2) The motor leads out the phase line and is grounded. The inspection method is the same as the first item of the fault.
3) Capacitor short circuit. Determine by measuring the DC resistance between the two ends of the starting winding circuit (including capacitors and starting windings, excluding centrifugal switches) using a multimeter with a lower resistance range (e.g. R × 1 range).
4) The centrifugal switch is short circuited to ground. The inspection method is the same as item 1).
5) Overloaded. The sound will be abnormal and the current will be greater than the rated value.
 
4. After starting the motor, the speed is lower than the normal value
1) There is a short circuit fault between turns or to ground in the main winding. The inspection method is the same as item 1) in section 3.
2) There is a coil reverse connection fault in the main winding. The sound will be abnormal and the current will be greater than the rated value.
3) The centrifugal switch is not disconnected, preventing the auxiliary winding from disconnecting from the power supply. The current will be greater than the rated value.
4) Heavy load or damaged bearings. The sound will be abnormal and the current will be greater than the rated value.
5) For series excited motors, short circuits between commutator segments or internal short circuits in armature windings, or poor contact between brushes and commutators.
 
5. When the electric motor is running, it quickly heats up
1) The winding (including the main winding and auxiliary winding) has a short circuit between turns or to ground. The inspection method is the same as item 1) in section 3.
2) There is a short circuit fault between the main winding and the auxiliary winding (outside the end connection point). The current will be greater than the rated value.
3) After starting, the centrifugal switch did not disconnect, preventing the auxiliary winding from disconnecting from the power supply. The current will be greater than the rated value.
4) For motors that primarily or solely rely on the main winding during operation (except for single value capacitor motors that start and operate with two identical windings), the main winding and auxiliary winding are misconnected to each other. The current will be much higher than the rated value.
5) The working capacitor is damaged or the wrong capacity is used.
6) The stator and rotor iron cores are rubbing against each other or the bearings are damaged. The sound will be abnormal and the current will be greater than the rated value.
7) The load is heavy. The current will be greater than the rated value.
8) For series excited motors, short circuits between commutator segments or internal short circuits in armature windings, or poor contact between brushes and commutators.
 
6. The operation noise and vibration of the electric motor are relatively high
Compared with three-phase asynchronous motors of the same capacity or chassis number, single-phase motors have relatively high noise and vibration (especially vibration). This is because its stator rotating magnetic field is not a regular circle, so the torque is not always equal, which means there will be fluctuations in magnitude within a circle, causing radial vibration of the rotor.
The common reasons for generating significant noise and vibration are as follows:
1) Poor paint immersion causes looseness between the iron core pieces and generates high-frequency electromagnetic noise.
2) The centrifugal switch is damaged.
3) Bearing damage or excessive axial movement.
4) Uneven air gap or axial misalignment between the stator and rotor.
5) There are foreign objects inside the electric motor.
6) For series excited motors, short circuits between commutator segments or internal short circuits in the armature winding, or poor contact between the electric brush and commutator (mica between commutator segments is higher than the commutator segments or the commutator segments are rough, or the electric brush is too hard or under excessive pressure, etc.).